This invention relates to laser gyros with mechanically dithered mirrors.
It has previously been proposed to avoid mode locking in laser gyros through the use of individually dithered or mechanically vibrated mirrors. In this connection, and as a general background reference, attention is directed to a text entitled "Laser Applications", edited by Monte Ross, Academic Press, Inc., New York, N.Y., 1971, in which pp. 134 to 200 relating to "The Laser Gyro" are to be noted, especially p. 159 which discusses "dithering" the mirrors of laser gyros. It has also been proposed to use a triangular laser path with three mirrors, in which the body of the laser with the attached mirrors is mounted on leaf springs and oscillated about a central axis perpendicular to the plane of the laser path. Such an arrangement is disclosed in NASA publication No. CR-132261, dated February 1973 for example, and in other published literature.
With regard to such prior proposals for the mechanical dithering of the mirrors of laser gyros, the individual oscillation of mirrors at high frequencies has been sensitive and relatively unstable and has produced results which have generally been inconsistent and unreliable.
On the other hand, the use of a triangular laser gyro path in which the entire triangular unit is vibrated or dithered about a central axis, has given adequate results, but has resulted in a gyro structure which is unduly cumbersome and oversize. In addition, the relatively high scattering resulting from the 30.degree. angle of incidence of the light on the mirrors has resulted in poor anti-lock characteristics, and has therefore reduced the sensitivity of such gyros. Also, undesired vibration has been transmitted to the case of the gyro.